Water quality in an urbanized river basin impacted by multi-pollution sources: From comprehensive surveys to modelling

The Seneque/Riverstrahler (SR) model, which was developed to establish links between the biogeochemical functioning of river systems and the constraints set by their (i) meteorology, (ii) drainage network morphology and (iii) human activities, was applied to the Day-Nhue River basin (DNRB). The DNRB is the most polluted area in northern part of Vietnam where domestic, industrial, agricultural and aquacultural activities have generated multiple sources of pollutants to the DNRB. Questionnaire surveys were conducted in industrial zones (at manufacturers and factories) of the DNRB to establish initial conditions of industrial activities for the SR. At the same time, water samples were collected from various industrial sectors and analyzed for suspended matter and nutrients. Additionally, river water quality surveys were conducted monthly at 11 stations inside the DNRB in 2006 and 2015. Simulation results from the SR model were then compared with analytical results of water quality for model validation. As a result, a nutrient budget of the river network was established to access the risk of coastal eutrophication in the Tonkin Bay. The model will provide adequate knowledge for policy makers to develop suitable water pollution management plans regarding nutrient sources and sinks.